Perfect solution, only requiring a small alteration!
Brad
I often wondered if a tapered bearing would be better suited seeing how the wheel is supported ONLY on one side.
Small tapered bearings are available.
A ball bearing is designed for rotational loads, not sideways.
It's not too late to change things. But it would have been nice if these valid points would have come up earlier.
Be that as it may, I can redo the whole spindle set up (at a later time).
The reason I went with using a head tube, ( I repeat myself here) is that this project started out to be a tandem bicycle build.
Thus not requiring the same load concerns as the present configuration.
I also thought that using bearings vs. no bearings would make steering easier.
If they really aren't that necessary then maybe something along the lines of the example below could be fabricated.

I could remove the bearing races, weld a top and bottom onto the headtube (with predrilled king pin holes).
I can make it adjustable for camber while I'm at it.
Make the 'U' bracket that would attach to the axle, and have a disc brake mount as well.
I think I could use my existing tie rod arms as well.
Like my drawing above. #698